Abstract: Objective: To investigate the competence of total antioxidation and scavenging reacticve oxygen radicals of Pinusmassoniana bark extract (PMBE) in different media and its effect on 8 human cancer cell lines cultured in vitro. Methods: Chemicalcolorimetry and measurement of tritiated thymidine incorporation (MTT) assay were applied to study the total antioxidationcompetence and reacticve oxygen radical-scavenging competence of PMBE in different media and its effect on human cancer celllines, respectively. Its antioxidative and reactive oxygen radical- scavenging competence was compared with that of naturalantioxidants vitamin C or vitamin E through chemical colorimetry. Results: PMBE owned higher competence of total antioxidationand scavenging reacticve oxygen radicals in normal saline in vitro, just a little less than VC and nearly 3.5 times as much as VE.Different inhibition degrees to different cancer cell lines with different concentration PMBE solutions were shown, respectively.Conclusion: PMBE would be a natural antioxidant and reactive oxygen radical scavenger, probably a functional potential forinhibiting cancer and could be applied in R&D of anticancer drug.

Key words: Pinus massoniana bark extract, antioxidant, reactive oxygen species, human cancer cell lines